Melting Front Evolution of Paraffin Wax Inside Metal Foams at Different Acceleration Levels

Phase Change Materials PCMs (e.g. paraffin waxes or fused silica salts) can be successfully used for the thermal management and the heat storage for ground and space applications. The PCM use is however limited by the low thermal conductivity of the melting material. Several methods have been proposed in literature to enhance the heat fluxes removed by the melting material. One of the most promising is to use of high conductive open cell metal foams embedded in the PCM material. The literature shows that the thermal behavior of this high conductive composite material (PCM/Foams) may be strongly influenced by the relative density and the pore size of the metallic foams because, as the melting process starts, natural convection can occur among the pores of the metal foams. The main goal of this work is to analyze the effect of different hyper gravity levels (up to 20g) and configurations (gravity direction parallel or perpendicular to the heat flux) on the melting performance of a composite aluminum foam/paraffin wax material. A transparent box allowed the synchronous visualization of the process in the visible and InfraRed spectrum simultaneously. The paraffin wax melting and solidification front is dynamically recorded at each acceleration levels (from normal gravity up to 20g). The role of natural convection among the heat transfer mechanisms involved in the melting process has been qualitatively explained. The average of the critical Rayleigh number for the different test cases is evaluated and discussed too.